You arrive on scene to find a 36-year-old male has wrapped his motorcycle around a street sign while traveling at a high speed. As you walk to where the patient is lying, you realize this is going to be a bad call. He is on the ground in full riding gear, including a helmet, and despite his leathers, you note blood and bubbles coming from the right side of his chest. You’re told that a well-meaning bystander pulled a shard of debris from the chest just prior to your arrival. Shortly after, the patient begins to complain of worsening shortness of breath and is now more drowsy, diaphoretic and confused. You cut away the jacket and note a large chest wound that is bubbling with each respiration.
The thorax includes all structures bounded by the thoracic inlet (a ring formed by the top of the sternum, the first thoracic vertebrae and the first ribs) superiorly, the diaphragm inferiorly, the sternum anteriorly and the vertebrae posteriorly. The chest wall is comprised of 12 pairs of ribs and the intercostal muscles. At rest, the ribs are angled downward as they track from posterior to anterior. Each rib is connected to the rib above and below it with a thin strip of muscle known as the intercostal muscle. The intercostal nerve, artery and vein run just below the lower surface of each rib.
The thorax can be divided into the mediastinum and two pulmonary cavities. The mediastinum contains the heart, esophagus, nerves, and several other vascular and lymphatic organs. Each pulmonary cavity contains a lung surrounded by two thin layers of connective tissue known as the pleura. A potential space exists between these layers known as the pleural cavity. Shortly after the trachea divides into the right and left mainstem (or primary) bronchi, these bronchi cross from the mediastinum into the pulmonary cavity.
They then divide into several subdivisions ultimately ending in the terminal bronchi and alveoli. Alveoli are balloon-like structures covered with capillaries. This arrangement allows for exchange of gasses such as oxygen and carbon dioxide.
The thorax is a dynamic body region. As we move, breathe and even age, the contents contained in the thorax change significantly. During flexion of the neck, the trachea slides down to become located entirely within the thorax. The esophagus normally runs through a hole in the diaphragm and connects to the stomach in the abdomen. However, in up to 50% of adults over the age of 50, a condition develops in which part of the stomach is pushed through this hole and into the mediastinum. This is known as a hiatal hernia.1 For this reason, damage to the stomach must also be considered in a penetrating thoracic injury. Due to the movement of the diaphragm during the respiratory cycle, the external landmarks are not reliable to determine the inferior border of the thorax. Thoracic or abdominal injuries are a possibility whenever there is an injury to the lower half of the chest.
Our respiratory cycle is dependent on the tendency of air to flow from an area of higher pressure to an area of lower pressure. As we inhale, our diaphragm lowers, flattening from its normally domed position. At the same time, the scalene and intercostal muscles flex, lifting the ribs upward and outward. These combined actions result in a pressure within the lungs relatively lower than the surrounding environment. This causes oxygen-rich air to flow from the relatively higher-pressure environment through the mouth and/or nose into the trachea and bronchial tree and ultimately into the sac-like alveoli. This is where oxygen is loaded onto the hemoglobin and the carbon dioxide is removed from the blood.
As we exhale, the natural recoil of the lungs, gravity acting on the ribs, and the return of the diaphragm to its relaxed, dome-shape state result in a higher pressure within the lungs. This expels oxygen-poor air up through the respiratory tree, out of the mouth and nose and into the environment.
Recognizing Chest Trauma
There are numerous types of possible thoracic injuries. Although some require further diagnostic testing after arriving at the hospital and may require specialized surgical treatment, several injuries require recognition and immediate treatment in the prehospital setting. These injuries are closed pneumothorax, open pneumothorax, sucking chest wound, tension pneumothorax and flail chest.
A pneumothorax is a condition in which air leaks through a defect in the lung, the chest wall or both, and collects in the pleural space. Because of the natural recoil of the lung, this results in partial or complete collapse of the lung. There are several variations of pneumothorax depending on cause and physiology of disease. Patients with a pneumothorax, regardless of type, will present with respiratory distress, including dyspnea and tachypnea, and tachycardia. They may also have decreased or absent breath sounds on the side of the chest with a pneumothorax. Additionally, pain with breathing is a frequent complaint.
Traumatic pneumothoraxes are divided into open and closed types. An open pneumothorax occurs when there is open communication between the environment and the pleural cavity through the chest wall. A special type of open pneumothorax is a sucking chest wound. In the sucking chest wound, air is sucked into the thoracic cavity through the chest wall instead of into the lungs through the airways. This occurs because air follows the path of least resistance. When the hole in the chest wall approaches 66% of the width of the trachea, a sucking chest wound can occur.2 The average tracheal width in a male has been reported to be 17.7 ± 2.0 mm in one report and 20.9 ± 0.32 mm in another report. The average tracheal width in females has been reported to be 15.8 ± 1.8 mm in one report and 16.9 ± 0.25 mm in another.3–4 An easy way to remember this is that any wound roughly the size of a penny or larger can lead to a sucking chest wound. Patients with a sucking chest wound will present with the same general signs and symptoms common to all pneumothoraxes listed previously. In addition, the patient will have an open wound to the chest that will normally bubble blood with inspiration and expiration.
A closed pneumothorax is one that is associated with a trauma, either blunt or penetrating, in which the chest wall remains intact. This is often explained by a broken rib that punctures the lung tissue. Less commonly, a closed pneumothorax can be the result of a penetrating neck, upper extremity or abdominal injury in which a projectile tracks into the thoracic space but doesn't cause an opening in the chest wall. The signs and symptoms of a closed pneumothorax don’t differ much from other pneumothoraxes: respiratory distress and possibly decreased or absent breath sounds on the affected size.
Occasionally, chest wounds occur in an arrangement such that air is able to travel from the environment, through the chest wall and into the pleural space during inhalation, but is unable to escape during exhalation. Since air is trapped during each breath, a tension pneumothorax can develop quickly. This occurs as the pleural cavity continues to fill with air, pressing on the lung until it's fully collapsed. As the pressure continues to build, the collapsed lung and intrapleural-free air begin to push on mediastinal structures, including the inferior vena cava (IVC), superior vena cava (SVC) and heart. This results in the inability of blood to flow back into the right atrium of the heart, leading to cardiovascular collapse. A tension pneumothorax can occur when either an open or closed pneumothorax is present, but more commonly happens with a closed pneumothorax.
A patient with a tension pneumothorax will exhibit all of the signs discussed earlier. In addition, the patient will exhibit signs of shock, including hypotension. Distended neck veins will be present as well as tracheal deviation away from the affected side.
Another severe chest injury is the flail chest. A flail chest is the result of chest trauma in which three or more adjacent ribs are each fractured in two or more places. This results in a segment of chest wall that is functionally disconnected from the surrounding chest. As the patient attempts to inhale, the increasingly negative pressure within the chest pulls this “flail segment” inward, reducing the volume of air that flows into the lungs and compromising the patient’s ability to oxygenate the blood and remove carbon dioxide. A flail chest is often associated with blunt trauma directly to the lung with subsequent bruising of the lung tissue, known as a pulmonary contusion. Signs and symptoms can include respiratory distress or pain with breathing and a section of the chest wall that moves paradoxically relative to the rest of the chest wall during inspiration and expiration.
The complications of chest trauma are numerous and of varying importance, ranging from simple bruising to circulatory collapse and death. One of the more telling signs of chest trauma is subcutaneous emphysema. In this condition, air is pushed from the upper airway or the pleural cavity into the subcutaneous tissue. Subcutaneous emphysema can be found in the chest, neck, face and, at times, the abdominal wall. This air can be felt as a crackling sensation upon palpation of the skin and is known as crepitus. Although rarely dangerous in and of itself, it's often one of the first signs of pneumothorax in the unresponsive patient.
Vascular injuries can occur in penetrating chest trauma leading to a hemothorax, where the thoracic cavity fills with blood. This condition can occur even with minor vascular injuries. Amazingly, each half of the chest can hold about 1/3 of the total blood volume. Unfortunately, out-of-hospital treatment of a hemothorax is limited. Rapid transport and early surgical intervention is the definitive management of this condition.
Assessment & Treatment
The first and most important step in the management of the chest trauma is maintaining a high level of suspicion. After a pneumothorax has been suspected or identified, the next immediate step is to decide if a tension pneumothorax is present. The classic teaching is the presence of dilated neck veins, tracheal deviation, unilateral absent breath sounds, tachycardia and hypotension. Tracheal deviation, however, is a late finding and should not be used to eliminate the possibility of a tension pneumothorax. Should these findings be present, the chest must be decompressed immediately to prevent circulatory collapse. A simple closed pneumothorax requires no immediate treatment and is often not discovered in the prehospital setting.
Chest decompression is simply releasing the air trapped within the pleural cavity. The fastest means of doing this is by needle decompression. The Department of Defense’s Tactical Combat Casualty Care Guidelines May 2012 describes the procedure as being performed by placing a large-bore needle (ideally 14 gauge, or 8 cm in length) between the second and third intercostal space at the midclavicular line, just above the superior aspect of the third rib or into the fourth intercostal space at the anterior axillary line.5 To avoid damage to the intercostal nerve and artery, the needle should be placed just above the superior aspect of the rib much like you would put a book onto a shelf. The needle should be inserted perpendicular to the chest wall and not angled toward the mediastinum to avoid injuring any of the mediastinal structures. If successful (and the scene is quiet), the provider may hear a rush of air. The patient’s hemodynamics should improve rapidly.
Much debate exists about the proper location for needle decompression. In 2011, researchers demonstrated that in pig chest walls attached to healthy volunteers simulating battle field transport, anterior axillary decompression catheters were more often kinked than the midclavicular approach due to the patients’ arms being strapped to their sides.6 However, in the same journal issue, other researchers showed in their human cadaver study that providers successfully gained access to the pleural cavity in all attempts at the anterior axillary line. In the midclavicular approach, just less than half of the attempts failed. This data was further analyzed and showed that when assessed by gender, the procedure was successful in less than a quarter of attempts in females but in three quarters of attempts in males.7
Several studies have measured the chest wall thickness via computerized tomography (CT) or ultrasound. Although the conclusions in the articles were varying, the trend in data suggests that an 8-cm-long needle will successfully decompress the chest in either location in all but a limited minority of patients.8–12
Another type of injury, sucking chest wounds, are a dramatic wound pattern with a fairly simple out-of-hospital treatment: placing an occlusive dressing on the chest wound. Early treatment of a sucking chest wound included placing an air-occlusive dressing over the site and taping it on three sides. It was thought that this dressing prevented additional air from entering the pleural cavity during inhalation and allowed trapped air to escape from the untaped edge during exhalation. However, the time required to apply this dressing and the limited effectiveness of the adhesive to stick to a diaphoretic bleeding patient often resulted in dressing failure.
Because of these difficulties, the Asherman Chest Seal was developed. This single-step dressing includes a tube with a one-way valve that extends from the center to allow air to escape—similar to the three-sided dressing but with a reduction in the amount of time needed for application. An alternative approach to this dressing is to simply place a defibrillator pad on the wound. Although it doesn't allow for escape of pleural air, the pad’s adhesive resolves the problems of too much time needed to tape three sides of the dressing and failure of the adhesive to stick to the patient’s chest wall. In some tactical settings, this simple approach combined with repeated needle decompression or occasionally “burping” the dressing, is preferred over the other dressing types.
Field management of flail segments is limited unless associated with tension pneumothorax. If a flail segment and tension pneumothorax are both present, the chest should be decompressed with a needle. If the flail segment is large, the patient may not be able to generate sufficient tidal volume to oxygenate the blood even with the supplemental oxygen. Intubation and positive pressure ventilation may be indicated. If intubated, special attention should be placed on reassessment of the patient because of a high likelihood of a tension pneumothorax developing. Current in-hospital management of a flail chest includes aggressive pain control. This may be sufficient for small flail segments, which don't compromise breathing mechanics. Larger flail segments may require intubation and surgical repair of the fractured ribs.
The prehospital management of chest trauma starts with a thorough primary and secondary assessment of the patient. Particular attention should be focused on mental status, presence of equal chest rise and fall, respiratory adequacy, oxygenation, and chest deformity. In patients with penetrating trauma, special attention should be paid to the axilla because injuroes to that area are often missed and can lead to disastrous consequences.
The majority of chest wall injuries can be stabilized with supplemental oxygen, needle decompression, pain control and occlusive dressings. Some patients may require endotracheal intubation. Understanding the anatomy of the chest, the mechanics of breathing and the mechanism of injury will help to anticipate clinical deterioration and prepare for additional lifesaving procedures.
During the primary survey, you correctly identify that this patient is likely suffering from a sucking chest wound. You immediately place a chest seal on the wound after drying the skin. This appears to briefly improve the patient’s clinical status. Minutes later, you note that the patient is again having trouble breathing. You immediately pull a 14-gauge needle from your bag and decompress the chest, resulting in an audible rush of air. Leaving the catheter in place, you continue following your trauma protocol and uneventfully transport the patient to the nearest trauma center.
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